On Apr 14, 12:48*pm, charles wrote:
In article ,
* *Andrew Gabriel wrote:

In article ,
* *John Williamson writes:
Moonraker wrote:
I read recently that LEDs in cars are not as efficient as touted, it
seems they need cooling to work efficiently, so that may apply to the
home as well.
Indeed it does. The lighting industry got a very bad reputation
with the dishonest claims for CFLs, and LEDs started off even worse,
e.g. quoting efficiencies with the LED chip at 25C, which is only
going to apply if you run the thing in your freezer.

Sorry, but while you might get 25°F in your freezer, 25°C is a slightly
warm ambient temperature.

Thats the Temperature Junction, Tj, in the data sheets, which is
actually a tiny area less than 1mm ^2 heating rapidly as soon as
energised.

Astounding effiency can be demonstrated by a couple of difficult to
replicate outside of the lab ,er, strategies.

Measure the output in first few miliseconds of start up with a boosted
current.

Actively chill the heatsink, to get Tj to 25C means heatsink is going
to have to start colder.

Run the device at a tiny current lowering self heating effects then
supply the numbers for massage to marketing department....

Cheers
Adam

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